Coaxial phase shifter



Aug. 7, 1956 D. J. LE VINE COAXIAL. PHASE SHIFTER Filed Feb. 2, 1955 INVENTOR DON/4&0 (A if V/A E BY M AGENT COAXIAL' PHASE SHIFTER Donald J; Levine, Fairlawn,-,N. J., .assignor to. Inter.-

ley, N. J.',,a.corporation of national: Telephone and .TelegraphCorpor-atiom, Nut! Marylan Application Feb'ruary Z, 1955, Seria-FNo: 485727 8 Claims. (Cl..333..-3 1),

Thisinvention relates to-electrical phase-shifting de= vices, and moreparticularly to anonresonant' coaxial" phase shifter.

Various devices for shifting the-phase of an electro magnetic signal have been used heretofore. waveguide structure, a long tapered dielectric' slabmay be moved from one side-of the guide, transverseto the direction of propagation, toward =the-center ofthe'guide, thereby changing the phase velocity-in that part of the guide. Also, a line stretcher "may'beusedin whichthe electrical length of a transmission line is changed by varying the physical'length ofthe line; This-maybe accomplished by telescoping onesection-of the'line into the other, in a trombone-like manner. Similarly, variable resonant structures are known for varying-the'tuning' response of a high-frequency electric circuit, asshown, for example, in UL S. 2,641,708.

However, in all such devices as knownheretofore, varrousdisadvantages are present; Thus; havinga structure that is resonant tendsito" limit'the-broadband= edness of the electromagnetic wave energy that-maybe propagated through such a device; Furthermore, such devices are generally discontinuous in nature; that is; they are not capable-of giving a continuous; uniform-variation of phase in a cyclical-manner without resorting to the use of elaborate cam mechanisms or other-"complicated mechanical artifices. Even-where such=devices are-rc= ciprocating' in operation, discontinuities occur-at th'ebe= ginning and end of the cycle. Also; with' such devices, it'

is difficult to obtain any but'a simple'typeof-pliase-shift: It is an object of the present invention 'to provide a nonresonant coaxial structure for varyingthephaseof' a propagated electromagnetic signal:

It is a further object to provide such -astructure thatis readily adaptable'for providing cyclic phase-shifts'ofa" wide variety of forms-"and shapes:

It is-an important feature of this invention that a coaxial nonresonant structure is-provided in which thephase of'a propagated electromagnetic'signal is'varid-in a cyclic continuous manner by rotating a closed-loop dielectric member having a helically wound condt'rctordis'posedthereabout within a hollow conductor-coaxially disposed about this closed-loop member.

It is a further feature'th'at'by varying thewinding pitch of this conductor about the' dielectricmember,- various types of phase shift outputs maybe obtained:

Other objectsand features of'this in-ventiomwillbereadily apparent by reference to' thefollowing description taken in conjunction with'theidrawingsin'whichz Fig. 1 is a plan view partly in section of a toroidal;

member, wound in a uniformly variable maxirnunu minimum manner;

Fig. 1A shows several possible phaseshifttoutputsaohtained withthe .windingofFig, v1;

Fig. 2 .is. a plan. viewvpartly, in section :of. astoroidal: member, accordingtov this invention,- ,wound-.witha-. pitch increasing uniformly to amaximum value;

Fig. 2A shows ;a. sawtooth;wavefornrzobtainableiastan;

output from-Fig.2;

Referring to Fig. 1, a closed-loop dielectric member 1 preferably in the form of atoroidisshown with a connited States Patent Patented Aug. 7, 1956 doctor 2; for-"example, a ribbon-like material such as silver; wound"aboutthedilectricmember. The thick.- ness of this conductormay. be varied depending upon thedesired'electrical. characteristics. A hollow conductor S i di'sposed in' a' di'electrically spaced coaxial .relationshipabout the-dielectrio member '1' for a fixed length.

This hollow conductorhasflanged elements. 4 and 5 forming're-entrant end portions'of'the hollow conductor. A-coaxia-lline' with a-center'conductor 6; and an outer conductor 7 maybe physically attached to the hollow conductor" 3" for coupling" a propagated. electromagnetic signal thereto; The'centerconductor 6joins the flange 40f the hollow conductor 3 at a. point which is approximately a quarter wavelen'gtlr'distant from the ends of thGhOllOW conductor: Ina sirnilar'rnannenav coaxial line consisting of a center conductor 8v and an outer conductor 9may becoupled-tothe flanged portion 5of the hollow conductor 3 for coupling an electromagnetic signal from this'coaxia'lstructure'. The conductorZ may be'wound'about'the dielectric member. 1. in many. diffe'rentwaysdepending upon the waveform of thephase shift" desired. As illustrated in Fig; 1, the conductor Z-iswound in a mannensuchtthat itspitch is uniformly variabl-e about-thecircular axis of the toroid," increasing.

uniformly to a'maximumwalue and" then decreasing uniformlythereftom toarninimurrr value. Where the rate ofchangeof pitchvaries in a linear manner, the obtained-output will} be a' uniform, linear sawtooth wave.

as shown in-the uppercurve ofFi'g; 1A. Where the rate. of change of pitch of the helically wound conductor varies uniformly in a non-linear manner, such as, for example, in a sinusoidal manner, the sine wave output showmin thedower. curve of Fig. 1A wi'lLbe obtained.-. It shouldbe. recognized that. from a theoretical pointof view. the;- propagation. constantis. not simple mathe matical function of the winding pitch and the geometry of the phase-shift structure. However, over a limited, but eminently useful and practical, range of winding pitch and structure geometry, the propagation constant is substantially; proportion-ah to: the winding pitch' andhenceemayrbe: readilyrdetermined lusing the known theoretical relationships. Various means may be ernployed for producing a relative movement between the closed loop dielectric member 1 and? the hollow conductor 3. In general, av ring-drive mechanism Itlwith guide rollers 11- and12-maybeused for uniformly rotatingthe dielectric member withinthe hollow conductor.

InFi'g. 2 the dielectric member 13;.is. shownwith the conductor 14' wound.thereahoutwith a uniformly variable pitch increasing to a maximum value. Upon rotating-this-mernber13within the. hollow conductor 15,]

by-meansofdriving'mechanismlti'and guide rollers 17 and'-18-, a type ofsawtooth wavehaving. a gradual rise and a-sharp"drop, as'illustratedin Fig, 2A, will'be obtained. In thisiem'bodir'nent .ofjthe phase-shift structure, a'probe'19is shown" as disposed'in an opening ZG-for coupling-electromagnetic. signal energy to the coaxial considered suitable. Also, while the conductor wound about the dielectric member may be in the form of a wire, in general a ribbon or foil, made of materials such as copper or silver, is particularly convenient for winding purposes. Many of various known drive mechanisms may be used for rotating the helically wound dielectric member within the hollow conductor. Thus, a constant-speed motor with rim-drive mechanism, as used for phonograph turntables, is suitable for this purpose. It is apparent that the phase shift obtained is a function of the rate of change of pitch of the velocity of the dielectric member and of the relative dimensions of the dielectric member and coaxially disposed outer conductor. Thus, for low-frequency applications, a closer winding of the conductor about the toroid would be used and the physical dimensions of the toroid and hollow conductor would be increased.

It is an important feature of this invention that there is provided a relatively simple means of obtaining almost any of a wide variety of variations in phase. Thus, by control of the rate of change of pitch, almost any type of phase variation may be obtained subject only to mechanical limitations in winding. Thus, the conductor may be wound about the dielectric member so that an algebraically varying phase shift is obtained. Similarly, a trigonometrically or harmonieally varying phase shift may be obtained. Thus, where p represents the pitch of the winding and represents the angle about the circular axis of the toroid over which the change in electrical length occurs, that is the circumferential distance between the input and output of the electromagnetic signal energy, the following relationship may be employed:

deF

between the limits of 0 and 211-. This results in a linear phase shift and an output such as illustrated in the upper curve of Fig. 1A for the triangular wave is obtained. Where 2% K sin 0 a cisoidal, that is, a sinusoidal or cosinusoidal type of wave is obtained. For the sawtooth type of wave, using the equation i a" K1 and integrating positive value of 6 between the limits of O and 21 results in a sawtooth type of wave, and integrating positive values of K between 0 and 1r and negative values of K between 1r and Zr results in a triangular type of wave. From the foregoing, it is apparent that many waveforms may be readily determined by appropriate mechanical calculation. Although it is preferred to rotate the dielectric member at a constant speed, for certain applications it may be preferable to use a variable speed drive. Similarly, the outer conductor may be rotated if desired and the inner dielectric member maintained stationary. The direction of rotation is a matter of choice depending upon the manner of winding. While two types of electromagnetic couplings to the coaxial phase shifter have been illustrated, other types of coupling may also be used in a manner known to those skilled in this art. For certain applications, also, part of the toroid may be wound uniformly with no variation in pitch while other parts of the toroid may be wound with a uniform or non-uniform shifting of pitch. Also, while the coaxially disposed hollow conductor has been illustrated as extending over approximately 90 of the circular axis of the toroid, this may be varied depending upon the particular applications desired. This coaxial phase shifter may be used whenever coaxial lines are considered desirable or suitable for transmission purposes, for example, up to frequencies of the order of 10,000 megacycles per second. Its use at low frequencies is restricted only by the fact that the phase shifter increases in its physical dimensions, and, therefore, at very low frequencies, the structure may prove too bulky or special types of couplings may be required. It should be understood that while the phaseshift device described herein may be resonant at some frequency, within its useful operating range, this device operates in a nonresonant manner; that is, the phaseshift device described herein may be considered from an operational point of view to be resonant.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

I claim:

1. A coaxial nonresonant structure for varying the phase of a propagated electromagnetic signal comprising a closed-loop dielectric member, a conductor disposed helically with a varying pitch about said dielectric member for at least a section thereof, a hollow conductor disposed in dielectrically spaced coaxial relation about a given length of said closed-loop member, means to pro duce a relative movement between said closed-loop mem her and said hollow conductor, and means for coupling electromagnetic signal energy to and from said coaxial structure.

2. A coaxial nonresonant structure, according to claim 1, wherein the closed-loop dielectric member is ring shaped and wherein a ribbon-like conductor is disposed helically with a uniformly variable pitch about said dielectric member.

3. A coaxial nonresonant structure, according to claim 1, wherein the rate of change of pitch of the helically disposed conductor increases uniformly to a maximum value and then decreases uniformly therefrom.

4. A coaxial nonresonant structure, according to claim 3, wherein the rate of change of pitch of the helically disposed conductor increases uniformly to a maximum value and then decreases uniformly therefrom to a minimum value, said rate of change of pitch varying in a sinusoidal manner thereby producing a sinusoidal phase shift.

5. A coaxial nonresonant structure, according to claim 1, wherein the rate of change of pitch of the helically disposed conductor increases uniformly and linearly to a maximum value and then decreases uniformly and linearly therefrom to a minimum value.

6. A coaxial nonresonant structure for varying the phase of a propagated electromagnetic signal comprising a toroidal dielectric member, a ribbon-like conductor disposed helically with a continuously variable pitch about said dielectric member, the rate of change of said pitch increasing uniformly to a maximum value over approximately 180 of the circular axis of the toroid and then decreasing uniformly for the remaining 180 of the toroidal circular axis, a hollow conductor disposed in dielectrically spaced coaxial relation for about of said toroidal member, first coaxial means for coupling a propagated electromagnetic signal to said structure and second coaxial means for coupling said electromagnetic signal therefrom.

7. A coaxial nonresonant structure, according to claim 6, including means for moving said toroidal dielectric member relative to said hollow conductor.

8. A coaxial nonresonant structure, according to claim 7, wherein said hollow conductor has flanged elements disposed re-entrantly at end portions thereof and said coaxial coupling means are coupled to said flanged elements at a point approximately a quarter wavelength distant from the ends of the hollow conductor.

No references cited. 

